It is difficult to start an internal combustion engine with a fuel such as methanol which has very low vapor pressure characteristics at low temperatures. An impractical but common method to start and warm-up an engine using such a fuel at these low temperatures is to provide a second fuel just for starting and warming the engine. This second fuel has a higher vapor pressure characteristic. Such a dual fuel system is used experimentally and requires separate fuel tanks and fuel lines as well as a control to direct the use of the two fuels. That makes this solution unacceptable for general use. This is a reason that methanol based fuels have generally not been well received as a serious alternative for automobiles and trucks.
A partial solution to the low vapor pressure problem is the practice of blending fuels to raise its low temperature vapor pressure. An example of such a blend is a 15% gasoline--85% methanal fuel known as M85.
There are a number of earlier patents disclosing systems and apparatus to heat fuel prior to engine use at low temperatures. The U.S. Pat. Nos. 3,868,939 and 3,999,525 disclose apparatus to heat fuel prior to injection into the engine by means of a housing with a resistance heater.
The U.S. Pat. Nos. 1,223,124 and 3,648,669 disclose a device with a resistance heater located downstream from the outlet of a fuel discharge device.
U.S. Pat. No. 4,375,799 discloses a carburetor in which a fuel inlet is encircled by a resistance heater.
U.S. Pat. No. 4,378,001 discloses a throttle body in which an injector is mounted so as to spray fuel towards a heater located opposite to the injector outlet.